Nanoscale self-affine surface smoothing by ion bombardment

The topography of silicon surfaces irradiated by a 2-MeV Si + ion beam at normal incidence and ion fluences in the range 10 1 5 -10 1 6 ions/cm 2 has been investigated using scanning tunneling microscopy. At length scales below ∼50 nm, surface smoothing is observed; the smoothing is more prominent at smaller length scales. The smoothed surface is self-affine with a scaling exponent α=0.53′0.03.